Methods and apparatuses of this type, for fibrillating synthetic ribbons or synthetic films, which are first extruded from a thermoplastic material, are known in general and are used for the structuring of ribbons or films. In doing so, it is possible to design, in particular, the smooth surfaces of the ribbons or films with a longitudinally executed structure. A method of this type and an apparatus of this type are known, for example, from EP 0 003 490.
With the known method and with the known apparatus a film is extruded from a thermoplastic material in an extrusion process, and a multiplicity of ribbons is cut therefrom. After stretching, the ribbons are fibrillated.
The fibrillation is normally carried out through spiked rollers, as are known, for example, from EP 0 358 334. A plurality of pins are attached such that they extend outward from the circumference of the spiked rollers, such that the pins, when the ribbons are fed onto the spiked roller, penetrate the ribbons, and generate a longitudinal slit in the ribbons, depending on the wrapping of the ribbons on the spiked roller. Particular fibrillation structures can be cut in the ribbons by means of the number and offsetting of the pins on the circumference of the spiked roller.
With the known method and with the known apparatus it has been found that with an increasing thickness of the ribbons, an undesired increase in the tractive forces occurs, in order to enable the penetration and cutting of the ribbons. In extreme cases, the ribbons are simply pushed away from the pins, without the pins penetrating the ribbons. In particular with the production of grass fibers, increasingly, synthetic ribbons made of numerous material components are formed, such that different layer thicknesses having corresponding thicknesses of the overall layer are obtained. With multi-layer ribbons of this type, it has furthermore been established that imprecisely cut edges are formed, which result in a significant loss in the strength of the ribbons.